1. Field of the Invention
This invention relates to molding an automotive trim component having a rigid substrate, a flexible covering and integrally molded energy absorbers consisting of a plurality of ribs and columns hereinafter known as "energy absorbers". More specifically, the invention relates to an automotive door panel made having integrally molded energy absorbers that produce depressions in the substrate which are concealed by a decorative covering.
2. Description of the Related Art
Modern automotive interiors include components having energy absorbing features. Described in U.S. Pat. No. 5,421,925 is an interior door trim having an energy absorbing foam bolster. The foam is secured to a backing surface of the door panel to absorb energy from a lateral or side direction impact. The U.S. Pat. No. 5,641,195 describes a method of securing the foam bolster to the backing surface of the door. While foam materials are good energy absorbers, the cost and complexity of attaching the bolster to the panel have caused others to utilize molded plastic energy absorbers.
U.S. Pat. No. 5,641,195, teaches a trim component for concealing a structural member. The U.S. Pat. No. 5,641,195 teaches molding the component to have a plurality of energy absorbing ribs spaced relative to one another along a backing surface. The ribs deflect upon contact with the structural member to absorb energy. This construction was particularly well suited for the A, B, C and D pillars of a vehicle. While this construction was particularly well suited for these members, it was difficult to adapt to larger components such as vehicle doors. The ribs generally extend normal to the substrate wall. When the plastic material cools, it shrinks. Because the substrate is thicker in the region over the rib, this area shrinks more. This difference in wall thickness causes depressions commonly called `sink marks` on the appearance surface. Heretofore, the only way to avoid sink marks was to limit the thickness of the finger to less than 60% of the nominal thickness of the substrate. This was a limiting factor to utilization of energy absorbers on other components.
It has been proposed to include energy absorbing ribs on the backing surface of a vehicle door trim as shown in U.S. Pat. No. 5,433,478. This patent shows a series of ribs having differing heights to provide different rigidity. The patent appears to lack the tables referenced in the specification, but the drawings illustrate that some of the ribs are almost 100% of the nominal substrate wall thickness. This would cause sink marks on the decorative surface of the door. The U.S. Pat. No. 5,433,478 does not address how these sink marks could be reduced or concealed.
U.S. Pat. No. 5,636,866, builds on the disclosure of the U.S. Pat. No. 5,433,478 and is incorporated herein by reference. The U.S. Pat. No. 5,636,866 uses the drawings from the U.S. Pat. No. 5,433,478 to described how thin-walled ribs integrally molded with the door panel do not provide sufficient energy absorbing properties in a confined spaced. The U.S. Pat. No. 5,433,478 also describes the difficulties of producing the long, thin-walled ribs including filing the mold with plastic and ejecting the molded article. The U.S. Pat. No. 5,636,866 overcomes these difficulties by forming a separate box-like structure that is secured to either the door or the trim panel. The energy absorbing structure has thick, short ribs. The ribs provide good energy absorbing properties. Because the structure is molded separately from the door panel, the door does not suffer from the sink marks described. While this structure overcomes the undesirable properties of the U.S. Pat. No. 5,433,478 , it does not provide the low-cost easily manufacturable, one-piece panel of the present invention. The U.S. Pat. No. 5,433,478 necessitates a joining process where the energy absorbing structure is attached to the backing surface of the panel or to the structural member of the door inner.
It is desirable to manufacture a door panel having energy absorbing properties in a single operation. It is possible to produce automotive trim components, such as door panels, instrument panels and consoles, using a multi-layered structure comprising a rigid polymeric substrate layer and a decorative flexible covering. Low pressure molding, laminate injection molding or compression injection molding, is currently used in the manufacturing of these components to integrally mold the flexible covering to a surface of the substrate layer. An advantage of the low pressure molding process is that the layers can be molded simultaneously. No pre-forming of either the covering or the substrate is required.
It is possible to adapt the low-pressure molding process to include forming an energy absorber on a door panel. A single operation may fabricate both the door panel with decorative fabric and the energy absorber thus reducing the cost and complexity of the final article. The present invention overcomes the difficulties of the prior art to provide a low-cost, easily manufactured door panel having integral energy absorbing members including a polymeric decorative fabric.